Vertebral morphology and intracolumnar variation of the iconic and bizarre viperid snake Pseudocerastes urarachnoides (Serpentes, Viperidae).

We document in detail the vertebral morphology of the viperid Pseudocerastes urarachnoides, a snake from the Middle East that is famous for its extreme tail modifications with bizarre spider-like luring appendages and its caudal luring behavior that enables it to successfully prey on birds. With the aid of micro-computed tomography scanning on the holotype specimen of P. urarachnoides, we focus on the intracolumnar variation across the whole vertebral column. Interesting morphological features of the vertebrae of this species are highlighted in comparison to other viperids, particularly at the caudal vertebral portion; nevertheless, there is no evidence of any skeletal element underlying the bizarre spider-like luring appendages of the tail of P. urarachnoides. A discussion on the caudal lure and its bizarre tail scales for this peculiar species is provided.